package org.lex.ftp.util;

import java.util.List;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;

public class ThreadPool {
	private static final ExecutorService pool;
	static {
		pool = Executors.newCachedThreadPool(new DaemonThreadFactory());
	}

	private ThreadPool() {
		super();
	}

	public static synchronized void execute(Runnable command) {
		pool.execute(command);
	}

	public static synchronized <T> Future<T> submit(Callable<T> task) {
		return pool.submit(task);
	}

	// ====================================
	public static void shutdown() {
		pool.shutdown();
	}

	public static List<Runnable> shutdownNow() {
		return pool.shutdownNow();
	}

	static class DaemonThreadFactory implements ThreadFactory {
		static final AtomicInteger poolNumber = new AtomicInteger(1);
		final ThreadGroup group;
		final AtomicInteger threadNumber = new AtomicInteger(1);
		final String namePrefix;

		DaemonThreadFactory() {
			SecurityManager s = System.getSecurityManager();
			group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
			namePrefix = "pool-" + poolNumber.getAndIncrement() + "-thread-";
		}

		public Thread newThread(Runnable r) {
			// is this right that we create all pool-thread as daemon?
			Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
			if (false == t.isDaemon())
				t.setDaemon(true);
			if (t.getPriority() != Thread.NORM_PRIORITY)
				t.setPriority(Thread.NORM_PRIORITY);
			return t;
		}
	}
}
